16.1 Organic analysis

Question 1

Test for a double carbon bond in alkene

Answer 1

Add bromine water and shake
Turns from orange to colourless

Question 2

Test for aldehydes

Answer 2

Warm with Fehling’s solution
Turns from blue to red

Or
Warm with Tollens’ reagent
Silver mirror will form

Question 3

Test for a halogenoalkane

Answer 3

. Add NaOH and warm
This is so nucleophilic substitution occurs to release the halide ion

. Acidify with HNO3 (nitric acid) to react with any carbonate ions
. Then add silver nitrate solution

An Agx complex will form
So white precipitate with chlorine
Cream precipitate with bromine
Yellow precipitate with iodine

Question 4

Test for an alcohol

Answer 4

Add acidified K2Cr2O7 (potassium dichromate)
Turns from orange to green with primary or secondary alcohols

Also with aldehydes

Question 5

How to test for carboxylic acid

Answer 5

Add NaHCO3
And CO2 gas is formed

So bubble it through limewater and it will turn it cloudy